Segmented tire mold

ABSTRACT

A segmented tire mold having radially movable circumferentially spaced sliding center segments activated by sliding connections between an upper mold half and the segments in response to opening and closing of the mold.

This application is a 371 of PCT/US99/22799 filed Oct. 1, 1999.

TECHNICAL FIELD

This invention relates to segmented tire molds and especially to moldshaving center segments which are movable radially in response to openingand closing of the mold.

BACKGROUND OF THE INVENTION

Full segmented molds such as the mold shown and described in U.S. Pat.No. 5,585,064 provide for expanding and contracting segments, however,the segments are mounted on the top mold and must be lifted to retractthe segments. In addition to the added power required to lift thesegments, the wear on the parts is also a disadvantage of this type ofmold.

Other segmented molds, such as the mold shown in Great Britain Patent GB1,176,162 provide hinged segments with springs for retracting the hingepins of the segment. The tilt type segmented molds of this type do notprovide for loading an uncured tire without engaging the bridge work onthe segments. This is especially objectional for molds with curvedsegmental boundary designs where the mold segments must be retracted ina direction perpendicular to the vertical axis of the segments.

SUMMARY OF THE INVENTION

The present invention is directed to a segmented mold having radiallymovable center segments which are mounted on the lower mold half. Eachcenter segment has a slotted connection with a sloped surface of theupper mold half for retracting and then returning the segment to theregistered position for molding a tire. The slot in the center segmentis open at the top to permit opening of the mold without lifting of thesegment. A spring holds the center segment in a radially outwardposition against a stop in the lower mold half which positions the slotfor engagement with the upper mold half upon closing of the mold.

In accordance with one aspect of the invention there is provided asegmented tire mold having an upper mold half, a lower mold half andradially movable circumferentially spaced sliding segments characterizedby:

a. each of the sliding segments being mounted on the lower mold half forradial movement,

b. a disengagable sliding connection between the upper mold half andeach of the sliding segments for moving the segments radially of themold between an open retracted position and a closed molding position.

In accordance with another aspect of the invention there is provided amethod of vulcanizing a tire in a segmented tire mold having an uppermold half, a lower mold half and radially movable circumferentiallyspaced center segments in sliding engagement with the lower mold halfand slidably engagable with the upper mold half upon closing of the moldcharacterized by:

a. opening the mold by lifting the upper mold half away from and out ofsliding engagement with the center segments,

b. moving the center segments radially outward by the sliding engagementwith the upper mold half,

c. limiting the movement of the center segments radially outward by stopmeans on the lower mold half,

d. placing an unvulcanized tire on the lower mold half,

e. lowering the upper mold half in sliding engagement with the centersegments for moving the center segments radially inwards into engagementwith the tire upon closing of the mold,

f. applying heat to the tire mold to vulcanize the tire,

g. lifting the upper mold half for sliding the center segments radiallyoutward on the lower mold half, and

h. removing the tire from the tire mold.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of the lower mold half and the center segmentsembodying the invention.

FIG. 2 is a section of the mold embodying the invention taken along line2—2 in FIG. 1 with parts being broken away to show the plunger and coilsprings of the mold in the closed position.

FIG. 3 is a section like FIG. 2 showing the center segment in apartially retracted position.

FIG. 4 is a enlarged fragmentary sectional view of one of the centeringpin connections between the lower mold half and the upper mold halftaken along the plane of line 4—4 in FIG. 2.

FIG. 5 is an enlarged fragmentary sectional view of the lower mold halftaken along the line 5—5 in FIG. 1 showing the stop means and spring pinfor a center segment in the fully retracted position.

FIG. 6 is an enlarged fragmentary sectional view of the slidingconnection between the upper mold half and one of the center segmentstaken along line 6—6 in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a segmental tire mold 10 is shown having alower mold half 12, an upper mold half 14 and radially movable centersegments 16. The lower mold half 12 and the upper mold half 14 havesidewall forming surfaces 18 and 20 respectively. The center segment 16has tread forming surfaces 22, which are movable radially fordisengaging the mold 10 from the tire after vulcanization.

Each of the center segments 16 is slidably mounted on a T-bar 24,fastened to the lower mold half 12 by bolts 26 or other suitable means.Each T-bar 24 extends radially of the mold 10 and slides in a slot 27extending radially of the mold.

Each of the center segments 16 also have recesses 36 with end flanges 28for plungers 30 mounted in sleeves 32 mounted on the lower mold half 12and urged radially outward by coil springs 34 located between therecessed surface 36 in the lower mold half 12 and a flange 38 on theplunger 30. The coil springs 34 hold the center segments 16 in the fullyretracted position after mold half 12 is pulled away from the centersegments 16.

Referring to FIG. 6, a slot 40 is provided in a sloped surface 42 of thecenter segment 16 and has grooves 44 for receiving rollers 46 mounted ona shaft 48, supported by a bar member 50 which is bolted to the uppermold half 14 by a bolt 51. The slot 40 extends from a base surface 52 toa top edge 54 of the center segment 16. With this construction, liftingof the upper mold half 14 from the position shown in FIG. 2 to theposition shown in FIG. 3 provides for travel of the rollers 46 upwardthrough the grooves 44 pulling the center segments 16 radially outwardto the position shown in FIG. 3.

Referring to FIG. 5, stop means, such as bolts 56 are located on thelower mold half 12 at spaced apart positions for limiting the radiallyoutward movement of the center segments 16 beyond the partially openposition shown in FIG. 3 to a position where the upper mold half 14 islifted away from the lower mold half 12 and center segment 16 removingthe rollers 46 from the grooves 44. The bolts 56 hold the centersegments 16 in the position shown in FIG. 5 by springs 36 so that whenthe upper mold half 14 is lowered onto the center segment 16, therollers 46 will be in alignment with and enter the grooves 40 forclosing the mold 10.

Referring to FIG. 4, centering pins 58 are mounted in the lower moldhalf 12 at circumferentially spaced positions for registering in holes60 in the upper mold half 14 when the upper mold is lowered intoposition over the center segment 16 and lower mold half 12.

The upper mold half 14 has shoulder forming surfaces 62 adjacent thesidewall forming surfaces 20 and the lower mold half 12 has shoulderforming surfaces 64 adjacent the sidewall forming surfaces 18.Positioned between the shoulder forming surfaces 62 and 64 are the treadforming surfaces 22 on the center segments 16.

In addition to the lower mold half 12, upper mold half 12 and centersegments 16, the segmental tire mold 10 also includes means for heatingthe molds and lifting and lowering the upper mold half 14. Theseservices are well known in the art and are included in this disclosure,although not shown in the drawings or described herein.

In operation the segment tire mold 10 is opened by lifting the uppermold half 14 away from the center segments 16 and lower mold half 12causing the center segments 16 to retract to a partially open positionshown in FIG. 3. The springs 36 move the segments 16 to the fully openposition shown in FIG. 5. A green unvulcanized tire is then lowered intothe lower mold half 12 and the upper mold half 14 lowered so that thecentering pins 58 shown in FIG. 4 are registered in the centering pinholes 60. The grooves 44 in the center segments are then in position forreceiving the rollers 46 of the segment bars 50 in the slots 40 of thecenter segments 16. Further lowering of the upper mold half 14 from theposition shown in FIG. 3 to the position shown in FIG. 2 causes thetread forming surfaces 22 of the center segments 16 to move radiallyinward into the position shown in FIG. 2. During the closing of the mold10, the springs 34 are compressed by movement of the flange 28 radiallyinward against the plungers 30. The segmental tire mold 10 is then inposition for molding the tire upon the application of heat for apredetermined period of time.

After the tire is vulcanized, the mold 10 is opened by raising the uppermold half 14. This results in radially outward movement of the centersegments 16 due to the action of each T-bar 24 in each slot 27 of eachcenter segment. As the upper mold half 14 is lifted, the rollers 46attached to the upper mold half engage the surfaces of the slot 40 inthe center segments 16 urging them radially outward out of engagementwith the cured tire tread. The upper mold half 14 may then be liftedaway from the center segment 16 and lower mold half 12 for removal ofthe tire.

What is claimed is:
 1. A segmented tire mold having an upper mold half,a lower mold half and radially movable circumferentially spaced slidingsegments characterized by: a. each of said sliding segments beingmounted on said lower mold half for radial movement; and, b. adisengagable sliding connection between said upper mold half and each ofsaid sliding segments for moving said segments radially of said moldbetween an open retracted position and a closed molding position, saiddisengagable connection comprising a plurality of spaced T-bars mountedon said upper mold half and engagable with a slot in each of saidsegments.
 2. A segmented tire mold in accordance with claim 1 furthercharacterized by a spring being mounted in said lower mold half and inengagement with each of said sliding segments for holding said segmentsin said open retracted position.
 3. A segmented tire mold having anupper mold half, a lower mold half and radially movablecircumferentially spaced sliding segments characterized by: a. each ofsaid sliding segments being mounted on said lower mold half for radialmovement; and, b. a disengagable sliding connection between said uppermold half and each of said sliding segments for moving said segmentsradially of said mold between an open retracted position and a closedmolding position, said disengagable connection comprising a T-barmounted on said upper mold half in sliding engagement with a slot ineach of said sliding segments.
 4. A segmented tire mold in accordancewith claim 3 further characterized by said T-bar having rollers forengagement with surfaces of said slot for reducing the slidingresistance of said second sliding connection.
 5. A segmented tire moldin accordance with claim 1 further characterized by said lower mold halfhaving circumferentially spaced centering pins extending upwardly forregister in corresponding spaced-apart holes in said upper mold half. 6.A tire mold in accordance with claim 1 further characterized by stopmembers mounted on said lower mold half radially outward of said slidingsegments for limiting radial movement upon opening of said mold.